This invention pertains generally to ammunition supply indicating systems for firearms, and, more particularly, to mechanisms for counting, and displaying, the number of rounds available in the weapon for discharge by the user.
Various devices are known for counting the number of rounds discharged from a firearm. In order to ascertain the number of rounds available for discharge, the user of the weapon must know, or ascertain, the number of rounds available when the first round was fired and subtract the number discharged. An error in calculating the number of rounds available to the user can have disastrous repercussions, particularly when the weapon is used in a confrontational setting by a police officer or soldier.
U.S. Pat. No. 4,558,626, granted Dec. 17, 1985, to Rolf Bartolles, discloses a primer cartridge magazine that is removably mounted in the reciprocally movable slider 9 of a wedge-type breech mechanism of the gun. A spring 34 and a guide member 5 in the magazine bias a stack of primer cartridges 4 toward the bottom of the magazine. An insertion opening 14 and an ejection opening 15 are defined at the lower end of the magazine. The magazine has a pair of opposing side walls which define a widened top portion having a pair of indicating windows 20. An indicating disc 2 is rotatably mounted upon a shaft, and indicates, through the viewing windows, the number of primer cartridges in the magazine. Enlarged head 55 on one end of tension bar 6 is connected to a shaft 28 and a bore 26 on one indicating disc. The other end of the tension band is engaged within slot 51 and bore 50 of the guide member 5 , as shown in FIGS. 4 and 6. Consequently, the number of cartridges retained within the magazine is clearly indicated.
U.S. Pat. No. 3,552,053, granted Jan. 5, 1971, to K. W. Jarvis, discloses a mechanism for counting the shots fired from a gun such as an M-16 rifle. The device consists of a frame 21 that is clamped to a gun barrel 11, in the manner shown in FIGS. 1 and 2 of the patent. The frame includes a piezoelectric crystal 50 (see FIG. 3) which is stressed by the transient radial expansion of the barrel to produce electrical impulses which are sensed by a threshold detector 22 and counted in a register 100.
U.S. Pat. No. 4,146,987, granted Apr. 3, 1979, to C. M. Hudson and William L. Andre, discloses a counter 2 used to record the number of rounds fired from large-caliber weapons systems. The counter includes a weighted mass 6 that is secured to shaft 4 so that the mass is freely pivotable in only one plane. A coiled spring 8 applies an opposing torque force of a constant, predetermined magnitude to the shaft so that the counter is activated only in response to a resultant torque force of a predetermined magnitude.